Mesoscale Precipitation Discussion 0119
NWS Weather Prediction Center College Park MD
452 AM EDT Sat Apr 13 2019

Areas affected...Far NE TX...northern LA...southern AR

Concerning...Heavy rainfall...Flash flooding possible

Valid 130900Z - 131400Z

Summary...Warm air advection induced elevated convection could
training along a quasi stationary front early this morning
extending from far northeast TX into southern AR, poses a threat
for flash flooding morning.

Discussion...The GOES-16 clean IR loop showed bursts of convection
forming in the broad warm air advection pattern established over
portions of the southern Plains into the Lower MS Valley (with
cloud tops as cold as -72 C over far northeast TX). A 30 to 35
knot low level flow is pushing moisture along and over a frontal
boundary extending from northeast TX into northeast AR, with
precipitable water values over 1.25 inches being advected along
and south of the front.

Scattered storms along and south of the front are feeding on a
reservoir of 1500-2000 J/KG of MUCAPE located over eastern TX.
Thus far, the convection has been scattered, but as diffluence
ahead of a short wave crossing the region increases, the
convection coverage is expected to increase along and north of the
boundary through 13/12z.

The convection is expected to remain largely elevated through that
time, as the convective mode remains mainly hail driven, as
regional 13/06z soundings showed dry air in the mid levels. The
column is expected to moisten in the continued warm air advection
pattern, allowing the convection to become more driven by warm
rain processes. As this occurs, hourly rainfall rates could
approach 1.50 inches (per the most recent HRRR).

The propagation vectors are expected to back with time ahead of a
mid level short wave, which could promote training along and near
the front, especially across southern AR. The most recent HRRR
showed an axis of 2.00/3.00 inches of rainfall over this area, and
these amounts are attainable if training occurs. Three hour flash
flood guidance values across this region are generally over 3.00
inches, though the 14 day rainfall here as been as much as 200-300
percent of normal. In addition, the National Water Model shows a
fairly significant expansion of high streamflow over southern AR.

Based on this above, flash flooding is considered possible during
the morning hours.

Hayes

ATTN...WFO...FWD...JAN...LZK...MEG...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...

LAT...LON   34089550 34069553 34729191 34129107 32639231
            32199357 32099512 32379698 33349669